title	description	prev	type	id
Chapter 9: Quarto basics	Quarto is the next generation R Markdown. This chapter teaches the difference between Quarto and R Markdown, and the basic use of Quarto.	/chapter8	chapter	9

Quarto is an open-source scientific and technical publishing system built on Pandoc.
Quarto can be considered the next generation R Markdown, where you interweave your narrative text and code together, except Quarto has no dependency on R and designed from the grounds up to be multilingual.
Quarto is relatively new, with the first version released in July 2022, so you may not find as many examples in the wild.

R Markdown and Quarto are both products maintained by Posit PBC (formerly RStudio PBC). Quarto has been designed from the grounds up after years of experience by the Posit/RStudio team.
Quarto unifies some disparate, and sometimes inconsistent, elements built within the R Markdown ecosystem into a common standard without the dependence on R. For example, rmarkdown::html_document converted R Markdown to an HTML document, but bookdown::html_document2 was needed for figure and table numbering, blogdown or distill to create certain types of websites, and xaringan or revealjs for creating slides. Not all packages (e.g. xaringan) used Pandoc under the hood, therefore some Pandoc features were not available.
It's likely that the Posit team will invest more into developing Quarto so new features will mostly reside there instead of R Markdown.

Yes, it's still worthwhile learning R Markdown!
There are still far more documents available in R Markdown than in Quarto, and so you'll come across more examples in R Markdown.
Even if you switch to Quarto, there will be many who will continue to stick with (legacy) R Markdown documents. You'll need to occasionally read these, so being fluent in R Markdown helps.
There will be cases where learning R Markdown is not essential. In a similar vein, knowing how to use LaTeX is also helpful, but not essential, for PDF document outputs.

The file extension of a Quarto document is .qmd while the file extension of an R Markdown document is .Rmd.
A Quarto document is quite similar to R Markdown document with YAML to specify the document metadata and specifications, body to write narrative text and code, and code chunks with a variety of options. However, Quarto documents are not backward nor forward compatible as R Markdown documents. This means that changing the extension from .qmd to .Rmd, and vice versa, doesn't work.

Key changes in YAML

output is now format
self_contained is now embed-resources
No more _s; most keys now use - instead of _. E.g. keep_md is now keep-md.
Global chunk options, previously set by knitr::opts_chunk$set(), can now be set in the YAML under the top level YAML key execute. For example, knitr::opts_chunk$set(eval = FALSE, echo = FALSE) can be set in the YAML as:

---
execute: 
  eval: false
  echo: false
---

Not all chunk options are under execute. For example, fig.width and fig.height are set under specific formats like below. Notice that the . in the chunk option names are now replaced with -.

---
format: 
  html:
    fig-width: 8
    fig-height: 6
  pdf:
    fig-width: 7
    fig-height: 5
---

If you are using knitr engine, then you can specify the chunk options under it like below:

---
knitr:
  opts_chunk: 
    collapse: true
---

Key changes in code chunk options

As mentioned in the previous section, the global chunk options can be set in the YAML under the top level YAML key execute. You can still use knitr::opts_chunk$set() for knitr engine.
The results option is replaced as output.
There is an additional caching method with freeze.
Chunk options can (and in fact, preferably) be set within the chunk by prefixing with #| like below.

```{r}
#| echo: true
#| eval: true
2 + 2
```

Currently, the single best guide for Quarto is at quarto.org.